This invention relates generally to cutting apparatus and more particularly to ultra high pressure abrasive waterjet cutting apparatus for cutting nuclear reactor structural components.
Structural components within nuclear reactor pressure vessels (RPV) become irradiated, and those components nearest the reactor core become highly irradiated. When such structural components require removal from the RPV and replacement, the components must be unbolted or cut from their original position and then subsequently cut into smaller sections for shipping and final storage. Because these components are radioactive, they must remain underwater to provide radiation shielding to workers in the proximity of the reactor components. The cutting process used to cut these structural components into smaller sections must therefore be performed underwater.
Known cutting apparatus for cutting reactor internals typically include a gantry type bridge with a partially submersible mast/manipulator attached. The gantry bridge and submersible manipulator permits from three to five axis of motion for the cutting nozzle. The disadvantages of these known cutting apparatus are that the gantry type bridge needs to be mounted on existing rails in the reactor, or new rails have to be installed. Because the cutting apparatus is mounted above the reactor internal components, it interferes with overhead crane cables when the crane is used for handling cut pieces of the reactor internal components. Additionally, the cutting apparatus interferes with the service platform which is used by personnel over the cutting area for manipulating rigging and cameras. Additionally, there is a possibility of the gantry running over hoses and power cables. It is also known that the mast/manipulator has stability problems when used with an ultra high pressure waterjet nozzle because of the force applied by the reaction to the ultra high pressure waterjet.
It would be desirable to provide a cutting apparatus for cutting reactor internal component parts in a nuclear reactor that does not include a gantry type bridge mounted on rails above the reactor.
In an exemplary embodiment, an ultra high pressure abrasive waterjet cutting apparatus for cutting nuclear reactor structural components includes an ultra high pressure abrasive waterjet (UHP) cutting nozzle, movably coupled to a single axis manipulator, and a collection hood. The manipulator and the collection hood are configured to be positioned inside adjacent openings of a nuclear reactor top guide and/or a core plate so that the cutting nozzle is in alignment with the collection hood. The cutting apparatus also includes a support frame configured to engage the top surface of the top guide to support the apparatus. The manipulator is coupled to the support frame, and the collection hood is movably coupled to the support frame.
The manipulator includes a linear frame, a nozzle support plate movably coupled to the linear frame, and a motor operatively coupled to the nozzle support plate by a drive belt or ball screw. The motor moves the nozzle support plate along the linear frame. The cutting nozzle is coupled to the nozzle support plate.
The collection hood includes an elongate collection chamber having an elongate opening. The opening is located in the chamber so that the opening is in alignment with the cutting nozzle. The collection hood also includes at least one positioning cylinder coupled to the collection chamber and to the support frame. The at least one positioning cylinder is configured to position the collection chamber opening adjacent a top guide beam and/or a core plate beam. The collection hood further includes an outlet port configured to be connected to a water filtration system.
To cut up a reactor top guide, the ultra high pressure abrasive wateriest cutting apparatus is positioned in the reactor with the support frame resting on the top guide and the manipulator and collection hood in adjacent top guide openings. Typically, the manipulator and the collection hood are in a vertical position and are perpendicular to the top surface of the top guide. The positioning cylinders arc then activated to move the collection chamber into engagement with a top guide beam with the collection chamber opening adjacent the top guide beam and in alignment with the UHP nozzle on the opposite side of the top guide beam. The UHP nozzle is activated and the nozzle is moved from one end of the linear frame to the other end of the linear frame by activating the motor which moves the nozzle support plate along the linear frame. The abrasive containing UHP water jet cuts through the top guide beam enters the collection chamber through the opening adjacent the top guide beam. The water filtration system connected to the collection chamber outlet port filters the used abrasive and kerf material from the water before it is returned to the reactor.
The above described ultra high pressure abrasive waterjet cutting apparatus is supported by the reactor top guide or core plate, thus eliminating the need for a gantry type bridge and partially submersed mast/manipulator. The above described cutting apparatus does not interfere with overhead crane cables when the crane is used for handling cut pieces of the reactor internal components, or interfere with the service platform which is used by personnel over the cutting area for manipulating rigging and cameras. Additionally, because the collection chamber is an integral component of the cutting apparatus and is supported by the support frame, it is unnecessary to utilize separate collectors mounted separately to the reactor component being cut up.